It is well known in the prior art that a magnetic material will stabilize with a plurality of equally sized magnetic domains, half magnetized in one direction and the other half magnetized in an opposite direction, since this produces a minimum energy state in the absence of externally applied fields. The size of each domain is referred to as equilibrium energy domain size which is generally measured in microns. The equilibrium energy domain size is established by several energy factors including anisotropy energy, magnetostatic energy and domain wall energy. A more complete explanation of the phenomenon may be found in an article by C. Kittel, entitled The Theory of The Structure of Ferromamagnetic Domains in films & Small Particles which appeared in Physics Review, Vol. 79, 1946, page 965.
The concept of utilizing magnetic domains and polarized light to create a magneto-optic iron-garnet display has been taught in an article by B. Hill and K. P. Schmidt entitled "Fast Switchable Magneto-Optic Memory-Display Components" which appeared in the Philips Journal of Research, Vol. 33, Nos. 5/6, 1978, page 211.
The display device taught in the Philips' article describes how the occurance of domains in a magneto-optic iron-garnet wafer is temperature dependent. That is, at a certain temperature the sublattice magnetizations cancel each other with the result that the net magnetization of the film vanishes. At this temperature point it is not possible to change the domains since there is no net magnetization to act on.
Yet another article by J. P. Krumme, P. Hansen, and K. Witter entitled "Thermomagnetic Switching of Ferrimagnetic Garnet Films At Their Compensation Temperature" which appeared in the Journal of Applied Physics, Vol. 47, No. 8, August 1976, page 3681 describes the creation of domains within a group of materials which is temperature dependent.
While the creation of domains within many materials has been discussed in the literature, few materials have been discussed which lend themselves to the creation of large area single domains. In many devices, such as a display device, it is desirable to obtain a large area capable of supporting a single domain within that area which may be switched from one direction of magnetization to another but which remains stable in either direction. This bistability is essential. The material must be uniaxial. i.e., magnetizable only along a single easy axis. Further, the material should not require a biasing magnetic field to retain bistability nor should the stability be temperature dependent.